What are the advantage and disadvantages of Project From View unwrap method?
You might have a photo of an object in real life that you want to map onto a 3-D object.

So you align the 3-D object to be in the same angle/scale as in the photo and project from view it so that the photo gets a bit more depth than simply flat image being manipulated.

If you have a persons head photoed from different angles, you can stitch together the face using this method.

https://www.youtube.com/watch?v=sZDMFkj8GqA